Integrated circuit packages are presently in wide use in the electronics industry in various types of electronic equipment. Integrated circuit packages can be characterized as high density devices having a very high number of electrical circuit packaged therein in a very small area for performing various electronic functions. The circuits that are arranged in an integrated circuit package are not visible, and all that. is visible in an inspection of most such devices are the aligned, thin, external leads extending from the opposite sides of the package that allow it to be readily inserted into an integrated circuit socket. Some circuit packages are now available in a leadless configuration such as those described in U.S. Pat. Nos. 4,551,746 and 4,551,747.
During the manufacture of circuit packages or related electronic devices, the devices must be transferred to and from types of equipment for the performance of different manufacturing steps. Examples of typical manufacturing steps are: (1) preliminary testing; (2) burn in loading; (3) burn in unloading; (4) elevated temperature testing; (5) cold temperature testing; (6) date code and part number marking; (7) lead scanning inspection; (8) centrifuge testing; (9) lead forming; and (10) final inspection. A burn in unloading process and apparatus for performing that process are disclosed in U.S. Pat. No. 4,439,917.
The electronic devices are protected during handling
between the various manufacturing steps or processes by being held in protective storage tubes. These tubes usually hold about 25 to 50 devices and are closed or pinned at both ends to keep the devices from falling out during handling. When processing is complete, the devices are shipped to customers in the tubes. Most tubes are made of extruded plastics, with some made of aluminum or stainless steel and used during in-house processing.
A large electronic device manufacturer will process up to a million or more devices per day. However, the devices are generally processed in lots averaging less than 3,000 devices in number. Assuming an average of 25 devices per tube, each lot will consist of around 120 tubes. One lot of tubes is normally stored in a bulk container called a "tote" box, which is transferred manually, along with related paperwork, between separate manufacturing processes.
Before performing a process step, the operator must individually pick up each tube from the tote box, remove the closure or stop pin from one end of each, tube and feed the devices into the process equipment. Upon completion of the process step, the operator must replace the closures or stop pins in each tube and return each tube to the tote box. Removal and replacement of the closures or stop pins is very time consuming. Therefore, many manufacturers attempt to transfer tubes between process steps with the closures or stop removed from one end. However, this leads to extensive damage of devices if tubes are dropped or accidentally turned wrong end up. When devices land on the floor, the package can be chipped or cracked or the leads broken or bent. In addition, when the operator must manually pick up devices from the floor, they can be damaged by electro-static discharge.
During any given process step, an operator must be present to load devices from and off load devices into tubes. This labor cost is a major part of the cost of manufacturing the devices. The operator can also cause damage to devices during handling by electro-static discharge or by accidentally dropping devices on the floor. Certain types of process equipment are able to operate on devices at speeds exceeding the rate at which an operator can manually feed devices to the equipment. Thus, either two or more operators are needed or the full speed capability of the process equipment cannot be utilized.
In summary, the current system of manually loading and off loading electronic devices to and from various manufacturing processes has some major disadvantages: (1) the labor cost is excessive; (2) the throughput is low; (3) the manual handling results in excessive damage to devices; (4) the equipment can be run only when an operator is present and must be stopped when the operator leaves; and (5) the high speed capacity of equipment is not fully utilized. A number of attempts have been made to automate or semi-automate tube handling to overcome these disadvantages. However, a number of problems must be addressed in automating tube handling.
An irregularly shaped tube must be selected from a bulk tote box holding many tubes. Not only do tube dimensions vary for tubes from different tube manufacturers, but they vary for tubes from the same supplier due to the inherent dimensional instability of the plastic extrusion process used to manufacture tubes. Once the tube is selected, it must be automatically oriented and rotated so that the devices are fed into or out of the tube with an orientation acceptable to the process equipment. When tubes are in bulk storage, their orientation and, in particular, their rotational position is random. The closure or stop pin must be removed from and replaced in one end of the selected tube. Most stop pins are plastic and are dimensionally predictable when made from the same injection mold. However, different pin suppliers make greatly different pin types so a pin pulling and insertion system must be able to handle various types of pins in a consistent manner. An automatic tube handling system should also be able to handle unexpected events without requiring operator assistance. Events such as: damaged or deformed tube ends; warped or twisted tubes; mixed batches of tubes from different suppliers; and devices that do not flow into or out of a tube.
Past attempts to automate tube handling involve semi-automatic means for loading and/or unloading devices where an operator still has to perform one or more vital functions. For example, some semi-automatic handling systems require the operator to select one tube from bulk storage, orient the tube, pull out the stop pin and place the tube in a chute or on a belt. All the semi-automatic handling systems require the operator to make most of the major decisions involved. These systems are not cost efficient and have not been generally accepted in the industry.
Past efforts at automating the selection of one tube from bulk storage have used "V"-shaped hoppers with various means for allowing the release of one tube at a time from the bottom of the hopper. These methods suffer from frequent jams caused by the irregular shape of the tubes and the tubes being compacted by the weight of the tubes in the hopper.
A number of approaches have been taken to tube orientation. Supporting a tube on air jets will cause it to orient in a particular position based on its center of gravity. Agitation of a tube until it fits into a mechanical reference to match a particular tube side will orient a tube in a particular position. Combinations of break beam sensors measuring two or more tube dimensions while the tube is being rotated will allow rotation to a particular position. All of these orientation methods are feasible to some extent when adjusted for a tube type having uniform dimensions. However, difficulties arise when tubes of varying dimensions are to be handled.
Stop pin removal is one area of tube handling where previous efforts have been limited to manually operated tools. A wedge type tool has been developed that works in a similar manner to the claw of a hammer. The stop pin is pulled out as the wedge is moved along the tube in a direction perpendicular to the length of the stop pin. However, this pin removal method is unsatisfactory because the side force on the pin can cause deformation of the tube around the hole in the tube that received the pin. This deformation can in turn impede the flow of devices into or out of the tube.
In addition, components, such as sockets, connectors, resistors, relays and switches, are increasingly being stored in tubes for protection during handling and shipping. Manipulation of these tubes between manufacturing steps or processes is likely to pose many of the same problems encountered with manipulation of circuit package storage tubes.
Accordingly, a need exists for a fully automated machine capable of selecting a single tube from bulk storage, orienting the selected tube to a particular position and removing the closure or stop pin at one end of the tube so that components can be fed into or out of the tube. The machine should be able to handle most unexpected problems without operator assistance and should be adaptable to interface with any number of different types of component processing equipment.